CN115458810B - Electrolyte and lithium ion battery - Google Patents

Electrolyte and lithium ion battery Download PDF

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CN115458810B
CN115458810B CN202211417646.0A CN202211417646A CN115458810B CN 115458810 B CN115458810 B CN 115458810B CN 202211417646 A CN202211417646 A CN 202211417646A CN 115458810 B CN115458810 B CN 115458810B
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electrolyte
carbonate
compound
lithium
toluenesulfonyl
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CN115458810A (en
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黄波
刘欣
杨小龙
梁大宇
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Gotion High Tech Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Secondary Cells (AREA)

Abstract

The invention provides an electrolyte and a lithium ion battery. The electrolyte comprises an organic solvent and LiPF 6 And additives including trifluoromethane sulfonic acid compounds and p-toluenesulfonyl compounds. The combined use of the trifluoromethane sulfonic acid compound and the toluenesulfonyl compound can form a stable interface film on the surfaces of the NCM ternary anode and the graphite cathode, and through the full synergistic effect of the trifluoromethane sulfonic acid compound and the toluenesulfonyl compound, the interface film is thin and compact, and the benzene ring structure of the toluenesulfonyl compound has great rigidity, so that the interface film is more stable, thereby improving the ion conductivity of the interface film, preventing the generation of harmful products such as HF and the like in electrolyte and the dissolution of cathode transition metal in the circulating process, further reducing the impedance of a lithium ion battery to a certain extent and improving the circulating performance of the lithium ion battery.

Description

Electrolyte and lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte and a lithium ion battery.
Background
In recent years, lithium ion batteries have become a new research hotspot and have received a great deal of attention. The field of electric automobiles is concerned with hybrid automobiles, mobile equipment power supplies, and the like, because of their high energy density, environmental friendliness, and economic friendliness. It is well known that cycle performance is one of the important indicators of batteries. As the battery continues to charge, it causes a continuous increase in internal resistance and generates a large amount of heat, often deteriorating cycle life over multiple cycles of charging.
Disclosure of Invention
The invention mainly aims to provide an electrolyte and a lithium ion battery so as to solve the problem of high impedance of the lithium ion battery in the prior art.
In order to achieve the above object, according to one aspect of the present invention, there is provided an electrolyte comprising an organic solvent, liPF 6 And additives including trifluoromethane sulfonic acid compounds and p-toluenesulfonyl compounds.
Further, the trifluoromethane sulfonic acid compound is a compound shown in a structural formula I:
Figure 449322DEST_PATH_IMAGE001
structural formula I
Wherein R1 is selected from the group consisting of silane groups, substituted or unsubstituted phenyl groups, substituted or unsubstituted C 1 ~C 4 Straight-chain alkyl, substituted or unsubstituted C 3 ~C 6 Preferably, the trifluoromethane sulfonic acid compound is selected from any one of branched alkyl groups
Figure 554681DEST_PATH_IMAGE002
、/>
Figure 441865DEST_PATH_IMAGE003
、/>
Figure 265465DEST_PATH_IMAGE004
、
Figure 529087DEST_PATH_IMAGE005
、/>
Figure 597275DEST_PATH_IMAGE006
Any one or more of the following.
Further, the trifluoromethanesulfonic acid compound is selected from the group consisting of
Figure 717678DEST_PATH_IMAGE002
、/>
Figure 169519DEST_PATH_IMAGE003
、/>
Figure 95886DEST_PATH_IMAGE004
Any one or more of the following.
Further, the p-toluenesulfonyl compound is a compound shown in a structural formula II,
Figure 51204DEST_PATH_IMAGE007
structure II
Wherein R2 is selected from cyano, halogen, ammoniaAny one of the groups, preferably the p-toluenesulfonyl-type compounds are selected from
Figure 670404DEST_PATH_IMAGE008
、/>
Figure 111006DEST_PATH_IMAGE009
、/>
Figure 982010DEST_PATH_IMAGE010
Any one or more of the following.
Further, the mass of the additive is 0.1-5wt% of the total mass of the electrolyte, and the mass ratio of the trifluoromethane sulfonic acid compound to the p-toluenesulfonyl compound is 1:5-5:1.
Further, the organic solvent includes any one or more of cyclic carbonate, chain carbonate and carboxylic acid ester, preferably the cyclic carbonate is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate and gamma-butyrolactone, preferably the chain carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate and ethyl propyl carbonate, preferably the carboxylic acid ester is selected from one or more of methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate and ethyl butyrate, preferably the organic solvent is selected from the combination of ethylene carbonate, diethyl carbonate and methyl ethyl carbonate, preferably the mass ratio of ethylene carbonate, diethyl carbonate and methyl ethyl carbonate is 1-2: 1-2: 2-5.
Further, the electrolyte further comprises a lithium salt additive, preferably the concentration of the lithium salt additive is 0.3-1 mol/L, and the lithium salt additive is preferably selected from lithium bis-fluorosulfonyl imide and LiBF 4 Any one or more of lithium bisoxalato borate, lithium difluorooxalato phosphate, lithium bistrifluoromethylsulfonyl imide, phenyl sulfone, tris (trimethylsilane) phosphite, vinyl sulfate, methyldisulfonate, and further, preferably, the lithium salt additive is a lithium bisfluorosulfonyl imide salt, vinyl sulfate, methyldisulfonate, or eugenolThe lithium salt additive is phenylsulfone, tris (trimethylsilane) phosphite, vinyl sulfate and methylene methylsulfonate.
Further, the above LiPF 6 The concentration of (2) is 0.5-1.5 mol/L, and preferably the electrolyte comprises: ethylene carbonate, diethyl carbonate and ethylmethyl carbonate, liPF 6 Vinyl sulfate, methylene methylsulfonate, lithium bis-fluorosulfonyl imide
Figure 916468DEST_PATH_IMAGE003
And->
Figure 581936DEST_PATH_IMAGE008
Wherein->
Figure 8369DEST_PATH_IMAGE003
2.5wt% of the electrolyte>
Figure 276540DEST_PATH_IMAGE008
0.5wt% of the electrolyte; or->
Figure 704985DEST_PATH_IMAGE003
0.5wt% of the electrolyte>
Figure 665987DEST_PATH_IMAGE008
2.5wt% of the electrolyte; or->
Figure 314138DEST_PATH_IMAGE003
0.8wt% of the electrolyte>
Figure 385999DEST_PATH_IMAGE008
2.2wt% of the electrolyte; or->
Figure 435994DEST_PATH_IMAGE003
1.2wt% of the electrolyte>
Figure 302319DEST_PATH_IMAGE008
1.8wt% of the electrolyte.
According to one aspect of the invention, a lithium ion battery is provided, which comprises a positive electrode plate, a negative electrode plate and an electrolyte, wherein the electrolyte is the electrolyte.
Further, the positive electrode sheet includes a positive electrode material, and preferably the positive electrode material is LiNi （1-x-y） Co x Mn y Wherein x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1.
By applying the technical scheme of the invention, the strong electron-withdrawing property of the trifluoromethyl in the trifluoromethanesulfonic acid compound enables the methylsulfonyl directly connected with the trifluoromethanesulfonic acid compound to have stronger reaction activity, and the trifluoromethanesulfonic acid compound can be used in combination with the toluenesulfonyl compound to form a stable interface film on the surfaces of the NCM ternary anode and the graphite cathode, and the interface film is thin and compact through the full synergistic effect of the trifluoromethanesulfonic acid compound and the p-toluenesulfonyl compound, and the benzene ring structure of the p-toluenesulfonyl compound has great rigidity, so that the interface film is more stable, thereby improving the ion conductivity of the interface film, preventing the generation of harmful products such as HF in electrolyte and the dissolution of cathode transition metal in the circulating process, further reducing the impedance of the lithium ion battery to a certain extent, and obviously improving the comprehensive performances such as the cycle performance of the lithium ion battery.
Detailed Description
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present invention will be described in detail with reference to examples.
As analyzed in the background art, the lithium ion battery in the prior art has the problem of high impedance, and in order to solve the problem, the invention provides an electrolyte and a lithium ion battery.
In one exemplary embodiment of the present application, an electrolyte is provided that includes an organic solvent, liPF 6 And additives including trifluoromethane sulfonic acid compounds and p-toluenesulfonyl compounds.
The strong electron-withdrawing property of trifluoromethyl in the trifluoromethane sulfonic acid compound enables the methylsulfonyl directly connected with the trifluoromethane sulfonic acid compound to have stronger reaction activity, and the trifluoromethane sulfonic acid compound can form a stable interface film on the surfaces of an NCM ternary anode and a graphite cathode when used in combination with the toluenesulfonyl compound, and the interface film is thin and compact due to the full synergistic effect of the trifluoromethane sulfonic acid compound and the toluenesulfonyl compound, and the benzene ring structure of the toluenesulfonyl compound has great rigidity, so that the interface film is more stable, thereby improving the ionic conductivity of the interface film, preventing the generation of harmful products such as HF in electrolyte and the dissolution of cathode transition metal in the circulating process, further reducing the impedance of a lithium ion battery to a certain extent, and obviously improving the comprehensive performances such as the circulating performance of the lithium ion battery.
In order to improve the film forming property of the trifluoromethanesulfonic acid compound, the trifluoromethanesulfonic acid compound is preferably a compound having the structural formula I:
Figure 703345DEST_PATH_IMAGE001
structural formula I
Wherein R1 is selected from the group consisting of silane groups, substituted or unsubstituted phenyl groups, substituted or unsubstituted C 1 ~C 4 Straight-chain alkyl, substituted or unsubstituted C 3 ~C 6 Preferably, the trifluoromethane sulfonic acid compound is selected from any one of branched alkyl groups
Figure 949868DEST_PATH_IMAGE002
、/>
Figure 713425DEST_PATH_IMAGE003
、/>
Figure 626017DEST_PATH_IMAGE004
、
Figure 373394DEST_PATH_IMAGE005
、/>
Figure 662424DEST_PATH_IMAGE006
Any one or more of the following.
To further increase the trifluoromethaneSynergistic interaction of sulfonic acid compound and p-toluenesulfonyl compound, preferably the trifluoromethanesulfonic acid compound is selected from the group consisting of
Figure 546066DEST_PATH_IMAGE002
、/>
Figure 160718DEST_PATH_IMAGE003
、
Figure 129811DEST_PATH_IMAGE004
Any one or more of the following.
In one embodiment of the present application, the p-toluenesulfonyl compound is a compound having the structural formula II,
Figure 189909DEST_PATH_IMAGE007
structure II
Wherein R2 is selected from any one of cyano, halogen and amino, and preferably the p-toluenesulfonyl compound is selected from
Figure 193637DEST_PATH_IMAGE008
、/>
Figure 448032DEST_PATH_IMAGE009
、/>
Figure 904421DEST_PATH_IMAGE010
Any one or more of the following.
The p-toluenesulfonyl compound containing the substituent groups has higher redox performance, and the synergistic interaction with the trifluoromethanesulfonic acid compound enables the p-toluenesulfonyl compound and the trifluoromethanesulfonic acid compound to generate thinner and denser CEI and SEI protective films on the surfaces of an NCM cathode and a graphite anode more easily, so that the cycle stability of the NCM cathode and the functionality of the graphite anode are greatly improved. On the other hand, the para-toluenesulfonyl functional group can inhibit LiPF 6 Thereby impeding the generation of harmful product HF and NCM during recyclingAnd the dissolution of the cathode transition metal further remarkably improves the cycle life of the NCM/graphite full battery.
Preferably, the mass of the additive is 0.1-5wt% of the total mass of the electrolyte, and the mass ratio of the trifluoromethane sulfonic acid compound to the p-toluenesulfonyl compound is 1:5-5:1, so that the synergistic interaction between the trifluoromethane sulfonic acid compound and the p-toluenesulfonyl compound is facilitated.
In an embodiment of the present application, the organic solvent preferably includes any one or more of cyclic carbonate, chain carbonate and carboxylic acid ester, preferably the cyclic carbonate is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate and γ -butyrolactone, preferably the chain carbonate is selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate and ethyl propyl carbonate, preferably the carboxylic acid ester is selected from one or more of methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate and ethyl butyrate, preferably the organic solvent is selected from a combination of ethylene carbonate, diethyl carbonate and methyl ethyl carbonate, preferably the volume ratio of ethylene carbonate, diethyl carbonate and methyl ethyl carbonate is 1-2:1-2:2-5.
The organic solvent of the type can better avoid the damage of water to the electrolyte, and is beneficial to promoting the more complete dissolution of each component in the electrolyte, thereby improving the synergy among the components and obtaining the electrolyte with excellent electrical properties.
In order to enhance the coordination between the lithium salt additive and the lithium salt and between the additives, thereby improving the comprehensive performance of the electrolyte, the electrolyte preferably further comprises the lithium salt additive, preferably the concentration of the lithium salt additive is 0.3-1 mol/L, preferably the lithium salt additive is selected from the group consisting of lithium difluorosulfimide salt and LiBF 4 Any one or more of lithium bisoxalato borate, lithium difluorooxalato phosphate, lithium bistrifluoromethylsulfonylimide, phenylsulfone, tris (trimethylsilane) phosphite, vinyl sulfate and methyldisulfonate, and further, preferably, the lithium salt additive is difluoroThe lithium sulfonimide salt, vinyl sulfate, methylene methylsulfonate, or preferably the lithium salt additive is phenylsulfone, tris (trimethylsilane) phosphite, vinyl sulfate, methylene methylsulfonate.
LiPF 6 As an electrolyte of the electrolyte solution, the conductivity, the energy storage property and the environmental protection property of the lithium ion battery can be enhanced, so as to further exert the LiPF 6 Is preferably LiPF 6 The concentration of (2) is 0.5-1.5 mol/L, and preferably the electrolyte comprises: ethylene carbonate, diethyl carbonate and ethylmethyl carbonate, liPF 6 Vinyl sulfate, methylene methylsulfonate, lithium bis-fluorosulfonyl imide
Figure 535254DEST_PATH_IMAGE003
And->
Figure 393488DEST_PATH_IMAGE008
Wherein->
Figure 84364DEST_PATH_IMAGE003
2.5wt% of the electrolyte>
Figure 28049DEST_PATH_IMAGE008
0.5wt% of the electrolyte; or->
Figure 698458DEST_PATH_IMAGE003
0.5wt% of the electrolyte>
Figure 411199DEST_PATH_IMAGE008
2.5wt% of the electrolyte; or->
Figure 132030DEST_PATH_IMAGE003
0.8wt% of the electrolyte>
Figure 703957DEST_PATH_IMAGE008
2.2wt% of the electrolyte; or->
Figure 676592DEST_PATH_IMAGE003
Is 1.2wt% of the electrolyte,/>
Figure 243840DEST_PATH_IMAGE008
1.8wt% of the electrolyte. Further, it is preferable that the mass ratio of ethylene carbonate, diethyl carbonate and ethylmethyl carbonate is 1:1:2, lipf 6 The concentration of (2) was 0.7mol/L, and the concentration of vinyl sulfate, methylene methylsulfonate and lithium difluorosulfimide salt were each independently 0.1mol/L.
In another exemplary embodiment of the present application, a lithium ion battery is provided, including a positive electrode sheet, a negative electrode sheet, and an electrolyte, the electrolyte being the foregoing electrolyte.
The lithium ion battery adopting the electrolyte has lower impedance and can obviously improve the comprehensive properties such as the cycle performance of the lithium ion battery.
In order to improve the cooperation of the electrolyte and the positive plate, thereby ensuring the performances of the lithium ion battery such as cycle stability, lower internal resistance and the like, the positive plate preferably comprises a positive electrode material, and the positive electrode material is preferably LiNi （1-x-y） Co x Mn y Wherein x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1.
The advantageous technical effects of the present application will be described below in conjunction with specific examples and comparative examples.
Compounds of formula I and formula II were purchased from the Ama Ding Shiji official network.
Example 1
Preparation of electrolyte (based on 1L electrolyte): mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) according to the mass ratio of EC to DEC to EMC=1:1:2, and adding 0.7mol of lithium hexafluorophosphate (LiPF) 6 ) 0.1mol of ethylene sulfate (DTD), 0.1mol of Methylene Methylsulfonate (MMDS), 0.1mol of lithium bis-fluorosulfonyl imide salt (LiFSI), and after the lithium salt is completely dissolved, 2wt% of the catalyst is added
Figure 135573DEST_PATH_IMAGE003
And 1wt%>
Figure 929216DEST_PATH_IMAGE008
。
Preparation of a positive plate: ternary material LiNi of nickel cobalt lithium manganate 0.7 Co 0.1 Mn 0.2 Uniformly mixing a conductive agent Super P, an adhesive PVDF and a Carbon Nano Tube (CNT) according to a mass ratio of 97.5:0.5:1:1 to prepare lithium ion battery anode slurry with certain viscosity, and coating the anode slurry on an aluminum foil for a current collector, wherein the coating amount is 360g/m 2 Drying at 85 ℃ and then cold pressing; then slitting, slicing, and then baking for 4 hours at the temperature of 85 ℃ in vacuum to prepare the lithium ion battery positive plate meeting the requirements.
Preparing a negative plate: the artificial graphite, the conductive agent Super P, the thickener CMC and the adhesive SBR (styrene butadiene rubber emulsion) are prepared into slurry according to the mass ratio of 95:1.5:1.0:2.5, the slurry is uniformly mixed, the mixed slurry is coated on two sides of a copper foil, and then the negative plate is obtained after drying and rolling, and then the negative plate meeting the requirements is prepared by drying for 4 hours at the temperature of 85 ℃ in vacuum.
Preparation of a lithium ion battery: the positive plate, the negative plate and the diaphragm prepared according to the process are manufactured into a lithium ion battery with the thickness of 0.5mm, the width of 8mm and the length of 10 through a lamination process, the capacity of 3Ah, the lithium ion battery is baked for 48 hours at the temperature of 85 ℃, and the electrolyte is injected to finish the battery manufacturing.
Examples 2 to 17 and comparative examples 1 to 4 the ratios and types of specific substances in the electrolytes were changed, and lithium ion batteries were obtained by referring to the preparation method of example 1, and the electrolyte formulations are shown in table 1 below.
TABLE 1
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Figure 360252DEST_PATH_IMAGE012
/>
Figure 688465DEST_PATH_IMAGE013
Example 10
Example 10 differs from example 4 in that,
0.83wt% was added
Figure 562881DEST_PATH_IMAGE003
And 0.17 wt%)>
Figure 142898DEST_PATH_IMAGE008
And finally obtaining the lithium ion battery.
Example 11
Example 11 differs from example 4 in that,
4.17wt% was added
Figure 684737DEST_PATH_IMAGE003
And 0.83 wt.%>
Figure 793639DEST_PATH_IMAGE008
And finally obtaining the lithium ion battery.
Example 12
Example 12 differs from example 4 in that,
the trifluoro methane sulfonic acid compound is
Figure 420929DEST_PATH_IMAGE002
Finally, the lithium ion secondary battery is obtained.
Example 13
Example 13 differs from example 4 in that,
the trifluoro methane sulfonic acid compound is
Figure 273479DEST_PATH_IMAGE004
Finally, the lithium ion secondary battery is obtained.
Example 14
Example 14 differs from example 4 in that,
the p-toluenesulfonyl compound is
Figure 669825DEST_PATH_IMAGE009
Finally, the lithium ion secondary battery is obtained.
Example 15
Example 15 differs from example 4 in that,
the p-toluenesulfonyl compound is
Figure 339841DEST_PATH_IMAGE010
Finally, the lithium ion secondary battery is obtained.
Example 16
Example 16 is different from example 4 in that the solvent is Ethyl Propionate (EP), and finally a lithium ion secondary battery is obtained.
Example 17
Example 17 is different from example 4 in that the lithium salt additive is 0.1mol/L LiFSI, 0.1mol of Phenylsulfone (PS) and 0.1mol of tris (trimethylsilane) phosphite (TMSP), and finally a lithium ion secondary battery is obtained.
(1) Initial direct current internal resistance (DCR) test
After capacity division, the experimental batteries in examples 1 to 17 and comparative examples 1 to 4 were charged to a state of charge of 50% soc, the sampling voltage V0 at the start of discharge was recorded after resting for 30min, then the sampling voltage V1 at the end of discharge was recorded after discharging for 10s at a current I of 2C, and the initial direct current discharge internal impedance dcr= (V1-V0)/I of the experimental battery was calculated.
(2) Cycle performance detection
The test batteries of examples 1 to 17 and comparative examples 1 to 4 were respectively subjected to charge-discharge cycle performance test at a charge-discharge rate of 1C under a test condition of 25C, the charge-discharge voltage interval was set to 2.8 to 4.25v, and the test results were shown in table 1 after being circulated for 800 weeks at normal temperature.
As can be seen from the comparison of the above examples and the comparative examples, the combination of the trifluoromethane sulfonic acid compound and the p-toluenesulfonyl compound of the present invention as an additive can greatly reduce the internal resistance of direct current of the lithium ion battery while significantly improving the cycle, as compared with the conventional additives.
From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:
the strong electron-withdrawing property of trifluoromethyl in the trifluoromethane sulfonic acid compound enables the methylsulfonyl directly connected with the trifluoromethane sulfonic acid compound to have stronger reaction activity, and the trifluoromethane sulfonic acid compound can form a stable interface film on the surfaces of an NCM ternary anode and a graphite cathode when used in combination with the toluenesulfonyl compound, and the interface film is thin and compact due to the full synergistic effect of the trifluoromethane sulfonic acid compound and the toluenesulfonyl compound, and the benzene ring structure of the toluenesulfonyl compound has great rigidity, so that the interface film is more stable, thereby improving the ionic conductivity of the interface film, preventing the generation of harmful products such as HF in electrolyte and the dissolution of cathode transition metal in the circulating process, further reducing the impedance of a lithium ion battery to a certain extent, and obviously improving the comprehensive performances such as the circulating performance of the lithium ion battery.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. An electrolyte is characterized by comprising an organic solvent and LiPF 6 And an additive comprising a trifluoromethanesulfonic acid-based compound and a p-toluenesulfonyl-based compound;
the trifluoromethane sulfonic acid compound is a compound shown in a structural formula I:
Figure FDA0004139768170000011
wherein R1 is selected from the group consisting of silane groups, substituted or unsubstituted phenyl groups, substituted or unsubstituted C 1 ～C 4 Straight-chain alkyl, substituted or unsubstituted C 3 ～C 6 Any one of branched alkyl groups of (a);
the p-toluenesulfonyl compound is a compound shown in a structural formula II,
Figure FDA0004139768170000012
wherein R2 is selected from any one of cyano, halogen and amino.
2. The electrolyte of claim 1, wherein the trifluoromethane sulfonic acid-based compound is selected from the group consisting of
Figure FDA0004139768170000013
Figure FDA0004139768170000014
Any one or more of the following.
3. The electrolyte according to claim 1, wherein the p-toluenesulfonyl-based compound is selected from the group consisting of
Figure FDA0004139768170000015
Any one or more of the following.
4. The electrolyte according to claim 3, wherein the mass of the additive is 0.1 to 5wt% of the total mass of the electrolyte, and/or the mass ratio of the trifluoromethanesulfonic acid compound to the p-toluenesulfonyl compound is 1:5 to 5:1.
5. The electrolyte according to claim 3, wherein the organic solvent comprises any one or more of cyclic carbonates, chain carbonates and carboxylic acid esters, the cyclic carbonates are selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate and gamma-butyrolactone, the chain carbonates are selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate and ethyl propyl carbonate, and the carboxylic acid esters are selected from one or more of methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate and ethyl butyrate.
6. The electrolyte according to claim 3, further comprising a lithium salt additive, wherein the concentration of the lithium salt additive is 0.3-1 mol/L, and the lithium salt additive is selected from the group consisting of lithium difluorosulfonimide salt and LiBF 4 Any one or more of lithium bisoxalato borate, lithium difluorooxalato phosphate, lithium bistrifluoromethylsulfonimide, phenylsulfone, tris (trimethylsilane) phosphite, vinyl sulfate and methyldisulfonate.
7. The electrolyte of claim 6 wherein the LiPF 6 The concentration of (2) is 0.5-1.5 mol/L, and the electrolyte comprises: ethylene carbonate, diethyl carbonate and ethylmethyl carbonate, liPF 6 Vinyl sulfate, methylene methylsulfonate, lithium bis-fluorosulfonyl imide
Figure FDA0004139768170000021
Wherein the said
Figure FDA0004139768170000022
2.5wt% of the electrolyte, said +.>
Figure FDA0004139768170000023
0.5wt% of the electrolyte;
or said
Figure FDA0004139768170000024
0.5wt% of the electrolyte, said +.>
Figure FDA0004139768170000025
2.5wt% of the electrolyte;
or said
Figure FDA0004139768170000026
0.8wt% of the electrolyte, said +.>
Figure FDA0004139768170000027
2.2wt% of the electrolyte;
or said
Figure FDA0004139768170000031
1.2wt% of the electrolyte, said +.>
Figure FDA0004139768170000032
Is 1.8wt% of the electrolyte.
8. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the electrolyte is the electrolyte of any one of claims 1 to 7.
9. The lithium ion battery of claim 8, wherein the positive electrode sheet comprises a positive electrode material, the positive electrode material being LiNi (1-x-y) Co x Mn y Wherein x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1.
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